Chain dependence

The kind of reaction which produces a dead polymer from a growing chain depends on the nature of the reactive intermediate. These intermediates may be free radicals, anions, or cations. We shall devote most of this chapter to a discussion of the free-radical mechanism, since it readily lends itself to a very general treatment. The discussion of ionic intermediates is not as easily generalized. 

Rea.CtlVltyRa.tlO Scheme. The composition of a copolymer at any point in time depends on the relative rates that each monomer can add to a chain end. If it is assumed that the chemical reactivity of a propagating chain depends only on the terminal unit and is not affected by any penultimate units, then four possible propagation steps in the copolymerisation of two monomers, and M2, with two growing chain ends, M and M2, can be written as follows ... 

Bioconcentration, Bio accumulation and Biomagnification. These aspects are determined by the physicochemical properties of a chemical, an organism s ability to excrete the chemical, the organism s lipid content and its trophic level. Bioconcentration relates to the difference between the environmental concentration and that of the body tissues. A high bioconcentration factor (BCF) predisposes to bioaccnmulation. The upper limit of bioaccnmulation is determined by lipid levels in the organism s tissues. Whether the resultant body burden causes biomagnification in the food chain depends upon the metabolic capabilities of the exposed organism. 

The Porter-Silber reaction, diagnostic for the dihydroxyacetone side-chain, depends upon prior Mattox rearrangement. " ... 

Chains drive function in essentially the same basic manner as belt drives. However, instead of tension, chains depend on the mechanical meshing of sprocket teeth with the chain links. 

Copolymerization occurred when the olefin had a basicity lower than that of the aldehyde (with respect to the initiator used), but sufficiently high occasionally to displace a molecule of initiator and give rise to an active species this situation produced copolymers with varying proportions of ether units in the chain, depending on the monomers feed ratio and on the olefin used. Isopropenylbenzene gave the best results with alternate copolymerization over a fairly wide range of feed ratios rt = 0.03 0.03, r2 = 0.4 0.1 (2-furaldehyde = Mj) indene produced copolymers with lower 2-furaldehyde contents. 

The Ziegler process produces linear alcohols with an even number of carbon atoms and is based on the polymerization of ethylene under catalytic conditions, generally with triethylaluminum as in the Alfol and the Ethyl processes. The distribution of alkyl chains depends on the version of the process employed but the alcohols obtained after fractionation can be equivalent to those obtained from fats and oils or have purpose-made distributions depending on the fractionation conditions. 

The copolymerization theory presented here assumes that the reactivity of a growing chain depends on the last mer added to the chain. Chemical theorists... 

The streptococci divide in only one plane. They grow normally in pairs or chains. Depending upon the species, the distal ends of each pair may be lancet-shaped, or flattened at the adjacent sides to resemble a coffee bean. 

PMMA can polymerise to form three different chains, depending on the tacticity of the chiral carbon in the chain. The isotactic (i-) and the syndiotactic (s-) forms are shown in Figure 4. 

Here x=qNb/6=qR where Ru is the radius of an undeformed Gaussian random flight chain. I deriving Eq. 10, the sum in Eq. 7 is replaced by an integral. The effect of the free chain segments, exclusive of the position of the junctions appears in the first two terms in the exponential. The deformations of the chains depend on the constraints on the junctions. Results are immediately derivable from Eq. 10. 

The decision as to where to locate the EDC unit in the vinyl chain depends on a number of complex factors. These must always be considered on a case-by-case basis. In this chapter the authors have attempted to provide a detailed overview of the impact of conceptually integrating the EDC unit within the chlor-alkali plant with a full summary of the benefits to the operator. 

Let us start our examination with the dpa-metal complexes. A series of trimetallic complexes of general formula [M3(dpa)4Cl2] (M = Cr,30 Ni,31 Co,32 Cu,33 Ru,34 Rh,34) have been structurally characterized. As illustrated in Scheme 2, such trinuclear complexes in the solid state can display either a symmetrical or an unsymmetrical M3 chain, depending upon if the metal-metal bond is extended over the three metal atoms, or is localized only between two metal atoms.35... 

Indices of order greater than two which can be computed as either path, cluster, path/cluster, or chain depending upon the configuration of the molecular fragments (Eqs. 41-47). 

The product distribution between reaction in the nucleus or in the side chain depends... 

When a chain has lost the memory of its initial state, rubbery flow sets in. The associated characteristic relaxation time is displayed in Fig. 1.3 in terms of the normal mode (polyisoprene displays an electric dipole moment in the direction of the chain) and thus dielectric spectroscopy is able to measure the relaxation of the end-to-end vector of a given chain. The rubbery flow passes over to liquid flow, which is characterized by the translational diffusion coefficient of the chain. Depending on the molecular weight, the characteristic length scales from the motion of a single bond to the overall chain diffusion may cover about three orders of magnitude, while the associated time scales easily may be stretched over ten or more orders. 

In a more general situation, the redox chain depends, among other factors, of the type of R produced by the fast H-abstraction (reaction 14). 

The relative rate of addition of ethylene to an aromatic side chain depends on the substituents present not only on the a-carbon but also on the aromatic nucleus. These effects have been studied using both p-dialkylben-zenes and mixtures of aromatics. 

In the third model (finite chain with different terminal groups) no reflection symmetry element exists in the Fischer projection. The individual macromolecules are, therefore, chiral and all the tertiary atoms are asymmetric and different. The stereochemical notation for a single chain, depending on the priority order of the end groups, can be R, R2, R. . . R -2, R -i, Rn or R, R2, R3... 

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